ON JANUARY 18, 2000, an estimated 23-foot- (7-meter-) wide, 250-metric-ton fireball as bright as the Sun streaked across the skies of western Canada and exploded with an estimated yield of 5—10 thousand tons of TNT. Scientists were able to pick up the remnants of the brilliant meteor—the first time freshly fallen meteor pieces were quickly recovered and brought to a lab untouched, on ice, and never thawed.

Most Pristine Meteorites Known

The Yukon meteor fragments were identified as carbonaceous chondrites, the most pristine, organically rich meteorites known. Carbonaceous chondrites are rare and difficult to recover because they are so fragile, easily breaking down during entry into Earth's atmosphere and during weathering on the ground. They comprise only about 2 percent of all meteorites known to have fallen to Earth.